<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      .flex-box {
        width: 500px;
        height: 500px;
        border: 3px dashed #f0f;
        display: flex;
        justify-content: center;
        align-items: center;
        /* flex-direction: column;
        flex-wrap: wrap; */
        /* flex-flow: wrap; */
        /* justify-content: space-evenly; */
        /* flex-wrap: wrap; */
        /* align-items: baseline; */
        /* align-content: space-evenly; */
      }
      .flex-item {
        width: 100px;
        height: 100px;
        background-color: #0ff;
      }
    </style>
  </head>
  <body>
    <div class="flex-box">
      <div class="flex-item">1</div>
    </div>
  </body>
</html>

